How long does it take for a turbine to 'pay back' the electricity used to manufacture it?

The comparison of energy used in manufacture with the energy produced by a power station is known as the 'energy balance'. It can be expressed in terms of energy 'pay back' time, i.e. as the time needed to generate the equivalent amount of energy used in manufacturing the wind turbine or power station.

It is estimated that the average wind farm will pay back the energy used in its manufacture within three to five months, and over its lifetime a wind turbine will produce over 30 times more energy than was used in its manufacture. As New Zealand wind turbines have an average-above capacity factor* - it is 20% to 30% higher than the world average capacity factor - the pay back time is probably even shorter in New Zealand. However this is faster than coal-fired power stations, which take about six months. When the energy used to supply the fuel for coal power plants is included, the energy balance for those conventional sources is clearly even poorer still, as coal-fired power stations continually produce C02.

*Capacity factor: In New Zealand the average capacity factor is between 40% and 50%. This means that over the course of a year the turbine would produce 40% to 50% of the amount it could theoretically have produce if it was working flat out all through the year.